Is read_file() always called after an activity __init__?

[Tomeu Vizoso]

On Thu, Feb 28, 2008 at 12:45 PM, Gary C Martin <gary at garycmartin.com> wrote:
> Hi Tomeu,
>
>
>  On 28 Feb 2008, at 09:40, Tomeu Vizoso wrote:
>
>  > Well, __init__ is too soon.
>
>  Well before calling activity.Activity.__init__(self, handle) yes that
>  would be a real bad idea for sure :-) but after that it 'should' be
>  fine shouldn't it, as the activity class is all set up? I can
>  certainly read the metadata in my main __int__ just after the call up
>  to super, and all works well.

You are right, though at some point we would like to defer the fetch
of data from the datastore to a later point after construction. In
this way some activities will be able to launch faster.

>  > AFAIK, the API docs say that you can
>  > safely access Activity.metadata in the read_file() and write_file()
>  > methods. read_file() is called when the user is resuming an existing
>  > activity and write_file() when sugar thinks it is a good time to save
>  > changes to the journal (probably several times during the life of an
>  > activity).
>
>  It does seem like read_file() is only triggered if you have previously
>  saved an actual file to filesystem, if you just have metadata, no call
>  is ever made to read_file() so it's a rather bad place to pick-up the
>  metadata. At least this is what I'm seeing here – I've just created a
>  0 size file in my write_file() and now a resume from that journal
>  entry is triggering read_file() every time.

You are right again. Perhaps we should add a read_metadata() method?
An alternative would be to have a 'datastore-loaded' method, but that
would be less consistent with the current API.

>  > Is very probable that the API documentation is lacking, can you point
>  > me to the docs you were following? Have you already read the HIG in
>  > the wiki?
>
>  Not an officially maintained page I know, but:
>         http://wiki.laptop.org/go/Beyond_Hello_World

Not that we have many officially maintained pages about sugar docs :/

>  Same suggestion comes from the current pydocs:
>         http://<xo_running_pydoc-p8080>:8080/
>  sugar.activity.activity.html#Activity-read_file
>         http://www.vrplumber.com/sugar-docs/sugar.activity.activity.html#Activity-read_file
>   (an online version)

Would be nice to have a wiki bot that would update the API docs in the
wiki from the sources. Anybody know something like that?

>  I also went through a number of activity sources in git looking for
>  examples, but I didn't find one that ONLY used metadata. They all seem
>  to either not bother storing any UI state (so resuming or from new
>  makes no difference), or they save actual files.

I think at some point activities like those realize that they have
some data that would be better saved in a file.

But the determining reason would be that metadata properties other
than the custom ones are not preserved across reboots :/

http://dev.laptop.org/ticket/4662

>  BTW: I'm quite happy with read_file() not getting called in file-less
>  cases, just a matter of documenting it somewhere (if that is indeed
>  the correct behaviour intended).
>
>  Thanks for your input.

Thanks,

Tomeu